REBOOT(8) BSD System Manager's Manual REBOOT(8)NAME
reboot, poweroff, halt — restarting, powering down and stopping the sys‐
tem
SYNOPSIShalt [-dlnpqvxz]
poweroff [-dlnqvxz]
reboot [-dlnqvxz] [arg ...]
DESCRIPTION
The poweroff, halt and reboot utilities flush the file system cache to
disk, send all running processes a SIGTERM, wait for up to 30 seconds for
them to die, send a SIGKILL to the survivors and, respectively, power
down, halt or restart the system. The action is logged, including enter‐
ing a shutdown record into the login accounting file and sending a mes‐
sage via syslog(3).
The options are as follows:
-d Create a dump before halting or restarting. This option is use‐
ful for debugging system dump procedures or capturing the state
of a corrupted or misbehaving system.
-l Suppress sending a message via syslog(3) before halting or
restarting.
-n Do not flush the file system cache. This option should be used
with extreme caution. It can be used if a disk or a processor is
on fire.
-p Attempt to powerdown the system. If the powerdown fails, or the
system does not support software powerdown, the system will halt.
This option is only valid for halt.
-v To enable verbose messages on the console, pass the boothowto(9)
flag AB_VERBOSE to reboot(2).
-x To enable debugging messages on the console, pass the
boothowto(9) flag AB_DEBUG to reboot(2).
-z To silence some shutdown messages on the console, pass the
boothowto(9) flag AB_SILENT to reboot(2).
-q Do not give processes a chance to shut down before halting or
restarting. This option should not normally be used.
If there are any arguments passed to reboot they are concatenated with
spaces and passed as bootstr to the reboot(2) system call. The string is
passed to the firmware on platforms that support it.
Normally, the shutdown(8) utility is used when the system needs to be
halted or restarted, giving users advance warning of their impending
doom.
SEE ALSOreboot(2), syslog(3), utmp(5), boot(8), init(8), rescue(8), shutdown(8),
sync(8)HISTORY
A reboot command appeared in Version 6 AT&T UNIX.
The poweroff command first appeared in NetBSD 1.5.
CAVEATS
Once the command has begun its work, stopping it before it completes will
probably result in a system so crippled it must be physically reset. To
prevent premature termination, the command blocks many signals early in
its execution. However, nothing can defend against deliberate attempts
to evade this.
This command will stop the system without running any shutdown(8)
scripts. Amongst other things, this means that swapping will not be dis‐
abled so that raid(4) can shutdown cleanly. You should normally use
shutdown(8) unless you are running in single user mode.
BUGS
The single user shell will ignore the SIGTERM signal. To avoid waiting
for the timeout when rebooting or halting from the single user shell, you
have to exec reboot or exec halt.
BSD February 16, 2011 BSD
